1. Field of the Invention
The present invention relates to a system and method for emergency access in Voice over Internet Protocol systems (VoIP), allowing limited communication connections when access is not otherwise authorized. Specifically, the present invention relates to a system and method for recognizing 911 emergency call requests and establishing and controlling a limited connection between the requesting device and server.
2. Description of the Related Art
A predominant goal of 911 access is the ubiquitous availability to emergency services. For both existing wired and wireless telephony services, 911 access is mandated from any device that has access to service, regardless of the user's subscription status or service restrictions.
For a wired telephone, when there is dial-tone present the network must permit a 911 call to be made. In the case of wireless telephones, if the handset can “see” the wireless system, the system must permit the handset to generate a 911 call. Both of these situations result as both networks can readily detect a request for a 911 call or a location specific Enhanced 911 (E911) call.
For Voice over Internet Protocol services (VoIP), providing 911 access without regard for service status is much more difficult. As can be appreciated by one skilled in the art, Voice over Internet Protocol is a communication technique for transmitting ordinary telephone calls over the Internet using packet-linked routes. A VoIP system captures, packetizes, and transports telephone conversations over a network, such as the Internet, which was originally designed to transport computer-generated data. However, because services such as VoIP are packet-based and use a layered protocol, VoIP communication systems require a software application on the device, such as a personal computer, to enable the device to make a call, and an IP services layer at the network to transport the call. The VoIP application can use one of several different signaling protocols, such as H.323, SIP, or Megaco, to initiate a 911 call and, as a consequence, a request for a 911 call may become embedded in a high-level protocol, which is not easily detected by the IP transport layer.
In providing 911 access, a VoIP client and IP services are assumed to be available and usable at the user device. Any additional capabilities required by the 911 service, such as user identification or caller location for enhanced 911 service (E911), are assumed to be provided by the VoIP client. Further details regarding E911 caller location services are set forth in IETF document entitled “Providing Emergency Call Services For SIP-Based Internet Telephony”, Jul. 13, 2000, the entire content being incorporated herein by reference.
The initial identification of 911 calls at a user device may involve the use of a special key on the user device, indicating a 911 call when pressed, or a predetermined key sequence, indicating a 911 call. Further details regarding identifying 911 calls at a user device are described in U.S. Pat. No. 6,073,005 entitled “Systems and Methods For Identifying Emergency Calls In Radio Communication Systems”, issued Jun. 6, 2000, the entire content being incorporated herein by reference.
Once a VoIP system 911 call is successfully initiated, existing call switching mechanisms can be used to complete the call. In most cases, a 911 call is merely switched from the IP network to a PSTN network for completion. Details regarding switching VoIP system 911 calls to PSTN networks are described in U.S. Pat. No. 6,363,065 entitled “Apparatus For A Voice Over IP (VoIP) Telephony Gateway And Methods For Use Therein”, issued Mar. 26, 2002, the entire content being incorporated herein by reference.
Providing VoIP system 911 call access without regard for service status may require bypassing multiple layers of security and access control in the network. For example, a device may have physical access to a network, such as a LAN, WAN or wireless system, but may not be authorized for IP services over the connection. Even if the device does have IP services available, it may not be authorized for access to the requested VoIP services or equipment. Arbitrary bypasses to security and access controls can be made to allow access, however, this can expose the network to theft of services or other potential attacks.
Accordingly, a need exists for a system and method for 911 access in Voice over IP systems in which 911 call requests are detected and restriction controls may be bypassed without compromising network security.